U.S. patent application number 09/865903 was filed with the patent office on 2002-11-28 for method to place a thermal interface when manufacturing an integrated circuit.
Invention is credited to Gektin, Vadim.
Application Number | 20020177306 09/865903 |
Document ID | / |
Family ID | 25346496 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020177306 |
Kind Code |
A1 |
Gektin, Vadim |
November 28, 2002 |
Method to place a thermal interface when manufacturing an
integrated circuit
Abstract
In accordance with the present invention, a method is described
which facilitates placement of a thermal interface on a thermal
lid. The thermal lid, which facilitates cooling, is placed on the
silicon layer after the silicon layer has been bonded to the
substrate layer. The thermal interface can be organic. In an
embodiment the thermal interface is metallic. In another embodiment
the thermal interface is an alloy. Placing the thermal interface on
the lid eliminates a step from the manufacturing process of the
package. In another embodiment an inorganic thermal interface is
placed on the silicon layer prior to bonding with the substrate
layer. The method also teaches using a thermal interface with a
melting point above a specified temperature. In a preferred
embodiment a melting point of greater than 62.degree. C. is
described.
Inventors: |
Gektin, Vadim; (San Jose,
CA) |
Correspondence
Address: |
HAMILTON & TERRILE, LLP
P.O. BOX 203518
AUSTIN
TX
78759
US
|
Family ID: |
25346496 |
Appl. No.: |
09/865903 |
Filed: |
May 25, 2001 |
Current U.S.
Class: |
438/678 ;
257/678; 257/E23.106; 438/122 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/3735 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
438/678 ;
438/122; 257/678 |
International
Class: |
H01L 021/44; H01L
021/48; H01L 021/50; H01L 023/02 |
Claims
What is claimed is:
1. A method of facilitating heat transfer from a silicon layer
during manufacture of an integrated circuit package, comprising:
providing a silicon layer; providing a substrate layer; bonding the
silicon layer to the substrate layer; providing a thermally
conductive lid; providing a thermal interface; operably disposing
the thermal interface on the thermal lid; and placing the thermally
conductive lid on the silicon layer.
2. The method as recited in claim 1, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 16.degree. C.
3. The method as recited in claim 1, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 62.degree. C.
4. The method as recited in claim 1, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 16.degree. C. and below 105.degree. C.
5. The method as recited in claim 1, wherein the step of providing
the thermal interface provides T-lma-60.
6. The method as recited in claim 1, wherein the step of providing
the thermal interface provides an alloy.
7. The method as recited in claim 1, wherein the step of providing
the thermal interface provides a thermal interface comprising: tin;
and lead.
8. The method as recited in claim 1, wherein the step of providing
the thermal interface provides a metal.
9. A method of facilitating heat transfer from a silicon layer
during manufacture of an integrated circuit package, comprising:
providing a silicon layer; providing a substrate layer; bonding the
silicon layer to the substrate layer; providing a thermally
conductive lid; providing a non-organic thermal interface. operably
disposing the non-organic thermal interface on the silicon layer;
and placing the thermally conductive lid on the silicon layer.
10. The method as recited in claim 9, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 16.degree. C.
11. The method as recited in claim 9, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 62.degree. C.
12. The method as recited in claim 9, wherein the step of providing
the thermal interface provides the thermal interface having a
melting point above 16.degree. C. and below 105.degree. C.
13. The method as recited in claim 9, wherein step of providing the
thermal interface provides an alloy.
14. The method as recited in claim 9, wherein the step of providing
a thermal interface provides an alloy, the alloy comprising: tin;
and lead.
15. The method as recited in claim 9, wherein the step of providing
a thermal interface provides a metal.
16. An integrated circuit package manufactured by a method,
comprising: providing a silicon layer; providing a substrate layer;
bonding the silicon layer to the substrate layer; providing a
thermal lid; providing a thermal interface; operably disposing the
thermal interface on the thermal lid; and placing the thermally
conductive lid on the silicon layer.
17. The method as recited in claim 16, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C.
18. The method as recited in claim 16, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 62.degree. C.
19. The method as recited in claim 16, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C. and below 105.degree.
C.
20. The integrated circuit package as recited in claim 16, wherein
the step of providing a thermal interface provides an alloy.
21. The integrated circuit as recited in claim 16, wherein the step
of providing a thermal interface provides a metal.
22. The integrated circuit as recited in claim 16, wherein the step
of providing a thermal interface provides T-lma-60.
23. The integrated circuit package as recited in claim 16, wherein
the step of providing a thermal interface provides an alloy, the
alloy comprising: tin; and lead.
24. An integrated circuit package manufactured by a method,
comprising: providing a silicon layer; providing a substrate layer;
bonding the silicon layer to the substrate layer; providing a
thermal lid; providing a non-organic thermal interface; operably
disposing the non-organic thermal interface on the silicon layer;
and placing the thermally conductive lid on the non-organic thermal
interface, wherein the non-organic thermal interface is operably
disposed on the silicon layer.
25. The method as recited in claim 24, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C.
26. The method as recited in claim 24, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 62.degree. C.
27. The method as recited in claim 24, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C. and below 105.degree.
C.
28. The integrated circuit as recited in claim 24, wherein step of
providing the thermal interface provides: tin; and lead.
29. The integrated circuit as recited in claim 24, wherein the step
or providing the thermal interface provides a metal.
30. The integrated circuit as recited in claim 24, wherein the step
of providing the thermal interface provides an alloy.
31. A computer system, comprising: a memory, a central processing
unit, the central processing unit manufactured by a method
comprising: providing a silicon layer; providing a substrate layer;
bonding the silicon layer to the substrate layer; providing a
thermal lid; providing a thermal interface; operably disposing the
thermal interface on the thermal lid; and placing the thermally
conductive lid on the silicon layer.
32. The method as recited in claim 31, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C.
33. The method as recited in claim 31, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 62.degree. C.
34. The method as recited in claim 31, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C. and below 105.degree.
C.
35. The integrated circuit as recited in claim 31, wherein the step
of providing a thermal interface provides an alloy.
36. The integrated circuit as recited in claim 31, wherein the step
of providing a thermal interface provides a metal.
37. The integrated circuit as recited in claim 31, wherein the step
of providing the thermal interface provides T-lma-60.
38. The integrated circuit as recited in claim 31, wherein the step
of providing the thermal interface provides an alloy.
39. The integrated circuit as recited in claim 31, wherein the step
of providing the thermal interface provides an alloy, the allow
comprising: tin; and lead.
40. A computer system, comprising: a central processing unit; and a
memory, the memory manufactured by a method comprising: providing a
silicon layer; providing a substrate layer; bonding the silicon
layer to the substrate layer; providing a thermal lid; providing a
non-organic thermal interface; operably disposing the non-organic
thermal interface on the silicon layer; and placing the thermally
conductive lid on the non-organic thermal interface, wherein the
non-organic thermal interface is operably disposed on the silicon
layer.
41. The method as recited in claim 40, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C.
42. The method as recited in claim 40, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 62.degree. C.
43. The method as recited in claim 40, wherein the step of
providing the thermal interface provides the thermal interface
having a melting point above 16.degree. C. and below 105.degree.
C.
44. The integrated circuit as recited in claim 40, wherein the step
of providing the thermal interface provides an alloy.
45. The integrated circuit as recited in claim 40, wherein the step
of providing the thermal interface provides a metal.
46. The integrated circuit as recited in claim 40, wherein the step
of providing the thermal interface provides an alloy, the alloy
comprising: tin; and lead.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to manufacturing integrated
circuits. More specifically, the invention relates to using a
thermal interface to promote even cooling of the silicon layer of
an integrated circuit.
[0003] 2. Description of the Related Art
[0004] Digital circuits, no matter how complex, are composed of a
small group of identical building blocks. These blocks can be gates
or special circuits or other structures for which gates are less
suitable. But the majority of digital circuits are composed of
gates or combinations of gates.
[0005] A microprocessor is a central processing unit of a computer
or other device using thousands (or millions) of gates, flip-flops
and memory cells. Flip-flops and memory cells are modified versions
of basic logic gates. Gates are combinations of high-speed
electronic switches.
[0006] It is known to manufacture an integrated circuit using
conductors separated by a semiconductor. Circuits are fabricated on
a semiconductor by selectively altering the conductivity of the
semiconductor material. Various conductivity levels correspond to
elements of a transistor, diode, resistor, or small capacitor.
Individual components such as transistors, diodes, resistors, and
small capacitors are formed on small chips of silicon. These
individual components are interconnected by wiring patterns
(typically aluminum, copper or gold).
[0007] An integrated circuit is then included in a larger
structure, known as integrated circuit package, that provides
electrical connections between the integrated circuit and the next
level assembly. The integrated circuit package also serves
structural functions. Integrated circuit packages are then mounted
on printed (or wired) circuit boards which are used to assemble
electronic systems such as personal computers and other data
processing equipment.
[0008] It is known to manufacture an integrated circuit package
using a layer of silicon and a layer of a substrate. Typically, a
substrate can be an organic material or a ceramic. Heat is applied
during the manufacturing process to bond the silicon layer to the
substrate layer. After bonding the silicon layer to the substrate
layer a lid (sometimes is referred to as a thermal lid) is attached
to facilitate the cooling process. The lid also provides structural
stability to the package.
[0009] The substrate layer can be ceramic or another material with
the necessary electrical conducting properties. Heat is applied
during the manufacturing process to bond the silicon layer to the
substrate layer. Uneven cooling of the silicon and substrate layers
(sometimes referred to as the "package") produces defects in the
package. Uniform cooling minimizes the number of manufacturing
defects in the package.
[0010] The thermal lid serves to conduct heat from the integrated
circuit package to the environment and thus facilitates even
cooling. The lid is typically formed from a metal due to the
thermal conductivity of metals. However, the thermal lid is
typically formed from a metal. Typically, neither the thermal lid
nor the silicon surface are sufficiently flat to provide an
efficient heat exchange interface. Thus, imperfections in the
surface of the thermal lid and the surface of the silicon prevent
complete surface contact between the surface of the silicon and the
surface of the thermal lid. The incomplete surface contact is an
impediment to heat transfer which in turn causes imperfections on
the silicon wafer.
[0011] To facilitate surface contact between the thermal lid and
the silicon surface a thermal interface is employed. The thermal
interface is organic and is not a solid. The thermal interface
(sometimes referred to as a thermal paste) can be applied to the
surface of the silicon before the thermal lid is attached. The
thermal paste is not a solid and can conform to imperfections in
the surface of the silicon. Similarly, the thermal paste can
conform to imperfections in the surface of the thermal lid. Thus,
using a thermal paste increases the surface contact between the
silicon and the thermal lid and promotes heat transfer.
[0012] It is known to employ a thermal interface which is organic.
Organic thermal interfaces are available which can be applied to
the silicon layer. Due to the difficulty of applying a metallic
thermal interface to the silicon layer, metallic thermal interfaces
are not used. Similarly, alloys exist which have superior thermal
conductive qualities to metals. For example, solder is a mixture of
lead and tin. Solder has superior heat conductive properties to
many metals. An alloy can also be used as a thermal interface.
Applying an alloy directly to a thermal lid avoids the problems of
applying the alloy to the silicon surface.
[0013] FIG. 1A depicts placing organic thermal interface 120 on
silicon layer 130. FIG. 1A depicts silicon layer 130 and substrate
layer 140 which combine to form package 150. FIG. 1B depicts
placement of thermal lid 110 on silicon layer 130. As shown,
substrate layer 140 is bonded to the opposing side of silicon layer
130 from organic thermal interface 121 and thermal lid 100.
[0014] FIG. 2 depicts the logical steps of placing organic thermal
interface 120 on the silicon layer. As shown in FIG. 2, the method
begins with start 210. From start 210 the logical steps include
providing substrate layer 230, providing silicon layer 220 and
providing thermal lid 240. After providing silicon layer 220 and
providing substrate layer 230 the silicon layer and substrate layer
are bonded 250. Provide thermal lid 240 is shown occurring prior to
bonding the silicon layer to the substrate layer 250 but in an
implementation can occur later. After providing thermal lid 240 the
organic thermal interface is placed on the silicon layer 260. After
the organic thermal interface is placed on the silicon layer 260
the thermal lid is placed on the silicon layer 270. After the
thermal lid and organic thermal interface are placed on the silicon
layer 270, the process ends 280.
[0015] As shown in FIG. 1B and FIG. 2, replacing the thermal
interface on the surface of the silicon is a step in the
manufacturing process. Each step in the manufacturing process
increases the cost of manufacture of the integrated circuit package
and introduces an opportunity for error. Eliminating steps from the
manufacturing process reduces the manufacturing cost.
[0016] In addition, each step in the manufacturing process which
can be eliminated also reduces opportunity for error. In the
instant example, error can be introduced by an excess of thermal
interface material or my uneven application of thermal interface
material. Either condition introduces an error into the
manufacturing process which can cause defects in the finished
product. Eliminating this step from the process reduces the
possibility of error. Reducing error reduces rejected components
and quality control time and thus reduces cost.
[0017] What is needed is a method of attaching a thermally
conductive lid to the silicon layer after bonding without the added
step of placing the thermal interface on the silicon layer. An
embodiment could include applying an inorganic conductive layer
directly to the silicon layer before the thermal lid is
attached.
SUMMARY OF THE INVENTION
[0018] In accordance with the present invention, a method is
described which facilitates placement of a thermal interface on a
thermal lid. The thermal lid, which facilitates cooling, is placed
on the silicon layer after the silicon layer has been bonded to the
substrate layer. The thermal interface can be organic. In an
embodiment the thermal interface is metallic. In another embodiment
the thermal interface is an alloy. Placing the thermal interface on
the lid eliminates a step from the manufacturing process of the
package. In another embodiment an inorganic thermal interface is
placed on the silicon layer prior to bonding with the substrate
layer.
[0019] The method also teaches using a thermal interface with a
particular melting point, or a melting point above a specified
temperature. In one embodiment a thermal interface with a melting
point greater than 16.degree. C. is used. In a preferred embodiment
a melting point of greater than 62 C is specified. Typically, the
melting point of the thermal interface used will be greater than
105.degree. C.
[0020] The foregoing is a summary and this contains, by necessity,
simplifications, generalizations and omissions of detail;
consequently, those skilled in the art will appreciate that the
summary is illustrative only and is not intended to be in any way
limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention may be better understood, and its
numerous objects, features and advantages made apparent to those
skilled in the art by referencing the accompanying drawings. The
use of the same reference number throughout the several figures
designates a like or similar element.
[0022] FIG. 1A depicts the related art of placing an organic
thermal interface on a silicon layer after the silicon layer is
bonded to the substrate. FIG. 1B depicts another step in the
related art, placing the thermal lid on organic thermal
interface.
[0023] FIG. 2 depicts a process flow diagram depicting logical
steps of the related art. Specifically, FIG. 2 depicts the logical
steps of the related art of placing an organic thermal interface on
the silicon layer before the thermal lid is placed.
[0024] FIG. 3A depicts placing a thermal interface on the thermal
lid. FIG. 3B depicts another step in the manufacturing process,
placing the thermal lid (with thermal interface) on the silicon
layer.
[0025] FIG. 4 depicts a process flow diagram depicting logical
steps of an embodiment. Specifically, FIG. 4 depicts the logical
steps of placing a thermal interface on the thermal lid and placing
the thermal lid (with thermal interface) on the silicon layer.
[0026] FIG. 5 depicts another embodiment. Specifically FIG. 5A
depicts placing an inorganic thermal interface on the thermal lid.
FIG. 5B depicts placing the thermal lid (with inorganic thermal
interface) on the silicon layer.
[0027] FIG. 6 depicts a process flow diagram depicting logical
steps of an implementation. Specifically, FIG. 6 shows the logical
steps of placing an inorganic thermal interface on the thermal lid
and placing the thermal lid (with inorganic thermal interface) on
the silicon layer.
[0028] FIG. 7 is a block diagram of a computer system. The computer
system incorporates various components (central processing unit,
memory, etc.) which are integrated circuits which may be
manufactured fabricated using the method taught.
DETAILED DESCRIPTION
[0029] The following sets forth a detailed description of a mode
for carrying out the invention. The description is intended to be
illustrative of the invention and should not be taken to be
limiting. A method is taught of placing a thermal interface on a
thermal lid during manufacture of an integrated circuit package.
Alternately, the thermal interface can be placed on the surface of
the silicon. In one embodiment, the thermal interface has a melting
point above 16.degree. C. In another embodiment, the thermal
interface has a melting point above 62.degree. C. In a preferred
embodiment, the thermal interface has a melting point above
16.degree. C. but below the melting point of package components
such as solder. The melting point of package components is
approximately 160.degree. C. Using a material with a melting point
above 16.degree. C. eliminates materials with melting points
substantially below room temperature. Similarly, using a material
with a melting point below 160.degree. C. eliminates materials with
melting points above the melting point of package components such
as silicon.
[0030] A material which is suitable for a thermal interface is
manufactured by Thermagon of Cleveland, Ohio. This specific
material, referred to as T-lma-60 has suitable thermal conductive
properties and can be used as a thermal interface when applied to a
silicon layer after the layer is bonded to a substrate. T-lma-60
can have more than one layer and is a thermal conductive structure
phase change material. T-lma-60 changes phase from solid to liquid
at approximately 60.degree. C. A thermal interface, such as
T-lma-60 or other, can have a plurality of layers. For example, a
thermal interface such as T-lma-60 can have three layers, one of
which can be a metallic central layer. According to one embodiment,
this material can also be applied to a thermal lid. The silicon lid
and thermal interface can be placed on the silicon surface after
the silicon is bonded to the substrate.
[0031] FIG. 3A depicts placing a thermal interface 121 on the
thermal lid 100. Thermal interface 120 can be organic or inorganic.
In an embodiment, thermal interface 120 is metallic. In another
embodiment, thermal interface 121 is an alloy, for example solder
which is a mixture of lead and tin. In another embodiment thermal
interface 120 can have layers. The layers can be organic, inorganic
or both organic and inorganic. FIG. 3A depicts silicon layer 130
and substrate layer 140 which combine to form package 150. FIG. 3B
depicts placement of thermal lid 110 and thermal interface 121 on
silicon layer 130. Substrate layer 140 is bonded to the opposing
side of silicon layer 130 from thermal interface 121 and thermal
lid 100.
[0032] FIG. 4 depicts the logical steps of placing thermal
interface 121 on the thermal lid 100. As shown in FIG. 4, the
method begins with start 410. From start 410 the logical steps
include provide substrate layer 430, provide silicon layer 420 and
provide thermal lid 440. After providing silicon layer 420 and
providing substrate layer 430 the silicon layer and substrate layer
are bonded 450. Provide thermal lid 440 is shown occurring prior to
bonding the silicon layer to the substrate layer 450 but in an
implementation can occur later. After providing thermal lid 440 the
thermal interface is placed on the lid 460. After the thermal
interface is placed on the thermal lid 460 the thermal lid is
placed on the silicon layer 460. After the thermal lid and thermal
interface are placed on the silicon layer 470, the process ends
480.
[0033] FIG. 5A depicts placing inorganic thermal interface 122 on
silicon layer 130. FIG. 5A depicts silicon layer 130 and substrate
layer 140 which combine to form package 150. FIG. 5B depicts
placement of thermal lid 110 on silicon layer 130. Substrate layer
140 is bonded to the opposing side of silicon layer 130 from
inorganic thermal interface 121 and thermal lid 100.
[0034] FIG. 6 depicts the logical steps of placing inorganic
organic thermal interface 422 on the silicon layer. As shown in
FIG. 6, the method begins with start 410. From start 410 the
logical steps include providing substrate layer 430, providing
silicon layer 420 and providing thermal lid 440. After providing
silicon layer 420 and providing substrate layer 430 the silicon
layer and substrate layer are bonded 450. Providing thermal lid 440
is shown occurring prior to bonding the silicon layer to the
substrate layer 450 but in an implementation can occur later. After
providing thermal lid 440 the inorganic thermal interface is placed
on the silicon layer 460. After the inorganic thermal interface is
placed on the silicon layer 460 the thermal lid is placed on the
silicon layer 470. After the thermal lid and organic thermal
interface are placed on the silicon layer 470, the process ends
480.
[0035] Integrated circuit chips formed by the method described
above can be used in many electronic devices including televisions,
radios, automobiles, data processing systems and computers systems.
In a computer system the integrated circuit can be a central
processing unit (cpu), memory or serve another function. A block
diagram of an example of a computer system is shown below.
[0036] An Example of a Computer System
[0037] The present disclosure is applicable to any integrated
circuit including data processing systems. Integrated circuits may
be found in many components of a typical computer system, for
example a central processing unit, memory, cache, audio controller,
network interface, I/O controller and I/O device as shown in the
example below. Integrated circuits are found in other components
within a computer system such as a display monitor, keyboard,
floppy and hard disk drive, DVD drive, CD-ROM and printer. However,
the example of a computer system is not taken to be limiting.
Integrated circuits are ubiquitous and are found in other
electrical systems such as stereo systems and mechanical systems
including automobiles and aircraft.
[0038] Referring to FIG. 7, computer system 730 includes central
processing unit (CPU) 732 connected by host buss 734 to various
components including main memory 736, storage device controller
738, network interface 740, audio and video controllers 742, and
input/output devices 744 connected via input/output (I/O)
controllers 746.
[0039] Typically computer system 730 also includes cache memory 750
to facilitate quicker access between processor 732 and main memory
736. I/O peripheral devices often include speaker systems 752,
graphics devices 754, and other I/O devices 744 such as display
monitors, keyboards, mouse-type input devices, floppy and hard disk
drives, DVD drives, CD-ROM drives, and printers. Many computer
systems also include network capability, terminal devices, modems,
televisions, sound devices, voice recognition devices, electronic
pen devices, and mass storage devices such as tape drives. The
number of devices available to add to personal computer systems
continues to grow, however computer system 630 may include fewer
components than shown in FIG. 7 and described herein. The
peripheral devices usually communicate with processor 732 over one
or more buses 734, 756, 758, with the buses communicating with each
other through the use of one or more bridges 760, 762.
[0040] Those of skill in the art will recognize that, based upon
the teachings herein, several modifications may be made to the
embodiments shown in FIGS. 1-7. For example, those skilled in the
art will recognize that incorporating integrated circuits
manufactured by the process shown in electrical systems other than
computers systems is incorporated in the spirit and scope of the
invention.
[0041] While particular embodiments of the present invention have
been shown and described, it will be recognized to those skilled in
the art that, based upon the teachings herein, further changes and
modifications may be made without departing from this invention and
its broader aspects, and thus, the appended claims are to encompass
within their scope all such changes and modifications as are within
the true spirit and scope of this invention.
* * * * *